Hydraulic fluids are defined as a liquid or mixture of liquids designed to transfer pressure from one point to another in a system on the basis of Pascal's Law.
Hydraulic fluids are used in many different types of production plants to operate the many different types of heavy equipment that shapes the product being produced into its desired form. Hydraulic fluid may leak from said hydraulic equipment onto surrounding equipment, building structures, and, in certain production processes, into the cooling water used to cool the product that is being produced. In all production plants, including production plants where the casting and milling of aluminum, steel, nickel, copper, brass or zinc takes place, it is desirable to minimize the amount of hydraulic fluid that leaks into the process cooling water system. Minimizing hydraulic fluid leaks into process cooling water in these systems offers a variety of potential benefits, including a reduced risk of microbiological growth outbreak caused by micro-organisms being able to feed and grow by digesting the hydraulic fluid, reduced variability of the process cooling water chemistry, reduced use of oxidizing biocides and reduced risk of process failures.
The costs associated with correction of hydraulic fluid leaks are due to added cost of replacing the hydraulic fluid which has leaked, system performance problems in the cooling water system where the hydraulic fluid has leaked, and metal casting problems due to reduced quality of cooling water such as plugging of spray nozzles, increased use of biocides, breakouts of hot metal during casting, and system shutdowns.
A current method of leak detection for hydraulic fluids is visual identification of a brightly colored hydraulic fluid showing up in contrast to its surroundings for leaks that occur onto surrounding equipment or building structures. The use of calorimetric detection, to detect a leak of hydraulic fluid into the cooling water system based on the visually detectable color of the dyes used, is known in the art to be insensitive and prone to interferences.
References that describe other techniques for leak detection of different types of fluids are as follows:
U.S. Pat. No. 5,304,800, entitled, Leak Detection and Responsive Treatment in Industrial Water Processes, describes and claims a process for detecting leakage from a process fluid to a temperature-conditioning fluid in an industrial process.
U.S. Pat. No. 5,320,967, entitled Boiler System Leak Detection, describes and claims a method of determining leakage from a boiler water system.
U.S. Pat. No. 5,416,323, entitled Leak Detection and Responsive Treatment in Industrial Water Processes, describes and claims a process for detecting leakage between a process fluid and a temperature-conditioning fluid in an industrial process wherein said industrial process includes an A and a B fluid, wherein one of said A and B fluids receives heat from or transfers heat to the other of said A and said B fluids by an indirect contact method, wherein one but not both of said A and said B fluids is an industrial process fluid, and wherein at least one of said A and said B fluids is a gaseous stream.
U.S. Pat. No. 5,658,798, entitled Detection of Process Components In Food Process Stream by Fluorescence, describes and claims a method for the monitoring of the variation in amount of fluorescing impurities during food processing in food process streams which contain fluorescing impurities.
U.S. Pat. No. 5,379,916, entitled Apparatus and Method for Determining the Concentration of Species in a Substance, describes and claims an instrument for determining the concentration of at least one species in a substance. The instrument and method can be used to identify and distinguish among various degrees of contamination of motor oil, diesel fuel, and hydraulic fluid by water, ethylene glycol, wear particles, and loss of anti-oxidants. The instrument includes a broad band light source, such as a tungsten filament incandescent lamp, which is very inexpensive and reliable. A fiber optic link is provided to a detector that receives and discriminates among optical spectral transmissions through the fiber optic. Discrimination circuitry is provided for evaluating the transmission and providing a readout that indicates the quality of the fluid. The instrument is suitable for in situ determination of oil quality.
U.S. Pat. No. 5,919,707, entitled Monitoring of Rolling Oil Emulsions, describes and claims a method for determining the concentration of an active ingredient contained in a rolling oil emulsion having two or more distinct phases at least one of said phases being liquid.
U.S. Pat. No. 6,165,384, entitled Full Spectrum Fluorescent Dye Composition for the Optimization of Leak Detection Process, describes and claims a fluorescent dye composition for inclusion in a working fluid for detecting sites of fluid leakage, the composition comprising a mixture of a perylene dye, a naphthalimide dye, and a hydrocarbon-based fluid, wherein the combination of the perylene dye, the naphthalimide dye and the hydrocarbon-based fluid are miscible in the working fluid, the working fluid being selected from the group consisting of heavy lubricants and transmission fluids and volumetric ratio of the perylene dye to the naphthalimide dye in the composition is in the range of from about 1.5:1 to about 5:1.
It is desirable to have an additional method for detecting and compensating for leakage of hydraulic fluids in a production plant.